1. The Field of the Invention
The invention relates to methods, means, and systems for archiving data. Specifically, the invention relates to methods, apparatus, and systems for efficiently recovering from disasters within virtual storage systems comprising removable media storage units.
2. The Relevant Art
Removable media libraries are used to store large amounts of computer data. The computer data is typically recorded on a plurality of removable media such as magnetic tape cartridges or optical disk cartridges. The plurality of cartridges may be housed in a system of storage bins which are accessible by an accessor mechanism, typically a robotic arm. The accessor mechanism moves the cartridges between the storage bins and the storage units or drives for reading and writing. In many systems, the activities of the accessor are controlled by a separate computer or server known as a library manager.
Computer data stored on the removable media are typically arranged in data volume units that originally corresponded to the storage capacity of legacy cartridges. The capacity of such storage media has grown substantially in recent years. Application software and system utilities written to use removable media libraries typically assume the smaller volumes in order to ensure backward compatibility with legacy systems. Thus, the average size of data volumes in most computer or data processing centers is significantly less than the capacity of the current removable media cartridges.
A virtual storage server (VSS) is a recent development that utilizes the full capacity of a current media by storing multiple logical data volumes onto a single physical (or stacked) volume. Data which would have been stored in multiple, mostly unused physical volumes are collected and stored onto “stacked” physical volumes as separately accessible logical volumes. Older physical drives are often emulated by virtual storage servers in a transparent manner to provide backward compatibility with legacy systems. Additionally, virtual storage servers often contain local storage drives and/or large memories which are used to cache logical volumes and thereby increase performance.
In order to properly manage access to both physical and logical volumes, certain information must be collected and managed within both the library manager and the virtual storage server. Typically, that information is stored in separate databases within the library manager and the virtual storage server, some of which may be redundant. In the event of disasters, information within the library manager and the virtual storage server databases must be rebuilt. Due to the amount of information involved and the slow access rate of physical volumes, a physical volume check-in process may consume several seconds per volume—which in large libraries results in disaster recovery sequences that require several hours of additional downtime.
What is needed are means and methods to reduce the duration of disaster recovery sequences. In particular, means and methods are needed to leverage the information that may be available within a virtual storage server database and thereby streamline a physical volume check-in process.